Vacuum device and method of exhausting same



Oct. 30, 1928. 1,689,297

H. c. RENTSCHLER VACUUM DEVICE AND METHOD OF EXHAUSTING SAME Filed Aug. 16, 192 2 INVENTOR HARVEY C QE/VTSCHLEE Patented Oct. 30, 1928.

UNITED STATES PATENT OFFICE.

HARVEY CLAYTON BENTSGHLER, OF EAST ORANGE, N EWJERSEY, ASSIGNOR TO WEST INGHOUSE LAMP COMPANY. A CORPORATION OF PENNSYLVANIA.

VACUUM DEVICE AND METHOD OF EXEAUSTING SAME.

Application filed August 16, 1922. Serial No. 582,261.

This invention relates to vacuum devices and more particularly to a method of exhausting and cleaning up the residual gases therein.

An object of my invention is to simplify the exhaust schedule for evacuated vessels by formin the same with a piece of aluminum or an a loy thereof, so located that it may be vaporized to exert an efficient clean-up action on the residual gases in the vessel.

Another object of my invention is the manufacture of evacuated devices, such as radio bulbs, incandescent lamps and the like, with a clean-up agent of aluminum, an alloythereof, or the same and another material, so located therein that it may be vaporized to efiiciently eliminate residualgases in the device.

A further object of my invention is the production of radio bulbs and the like by forming the same with a piece of foil or sheet consisting of aluminum or an aluminum alloy, attached to the plate thereof, cold-exhausting said bulb to obtain a moderate vacuum therein, efficiently eliminating the residual gases therein and, at the same time, heat-- treating the plate thereof by inductively heating the plate to vaporize the aluminum or a part thereof from the same.

' A still further object of my invention is the activation of aluminum, an alloy thereof or aluminum and another material such as magnesium or calcium, in a vacuum device, after a moderate exhaustion and tipping ofl ofthe same, whereby a high vacuum is produced therein.

Other objects and advantages of the invention will be made apparent by the following description.

In certain evacuated electron devices such as radio bulbs, X-ray tubes and the like, it is desirable to have a very high vacuum therein. If a device of this character is coldexhausted and sealed up, it is found that, upon actuating the same,

given off from various parts of the device, such as the Walls of the bulb, the plate and other metallic parts of the same. For thls reason, it has been customary to 'bake out the bulb and heat-treat the plate and other metallic parts of the device while the same is being evacuated on the pump, Such treatment on the pump is expensive and not en tirely satisfactory, in that it makes the occluded gases are process of exhausting the bulb unduly long and complicated, therebycuts down the production of such devices with a given amount of machinery and does not provide for the elimination of gases liberated when the device is tipped off.

Various attempts have been made to evacuate such devices while cold and remove or clean-up residual gases after tipping off. One of the materials tried as a clean-up agent was magnesium. A radio bulb, to the plate of which Was attached a small piece of magnesium foil or ribbon was cold-exhausted to a moderate degree, tipped ofi and the plate 1nd uctively heated until the magnesium was act vated by being vaporized, cleaning-up the residual gases in the bulb. The disadvantage of magnesium lies in the fact that it vaporizes at such a low temperature thatit will not stay on the plate long enough to subject the plate to the requisite .amount of heat-treatment to drive off occluded gases, before all of the magnesium will have vaporized and condensed on the walls of the bulb, thereby being rendered inactive for removing, absorbing or cleaning-up any occluded gases remaining in the plate.

Besides the above noted difliculty, magnesium is not as good a clean-up agent for hydrogen-as is desirable and is apt to produce a mirror-like coating on-the bulb, which will render it difficult or impossible to observe the contents of the bulb.

According to my invention, I exhaust vacuum devices such as radio bulbs and the like in the following manner. Prior to sealin the mount into the bulb, there is attach to the plate of the mount, preferably in inti mate contact therewith, a piece of aluminum, preferably in the form of a thin sheet or foil or a similar piece of material consisting largely of aluminum, such as an alloy or mixture of alummum and magnesium, aluminum and calcium, or apiece of magnesium, or other material such as calcium or phosphorus, together with a piece of aluminum. The advantage'of the last mentioned arrangement is that the magnesium will be activated more quickly than the aluminum, because it vblatilizes more readily and will, therefore,

exert a clean-up or absorbent action-on the residual gases priorto the activation of the aluminum and thereby prevent the formation of as high a pressure as would be generated in the device if aluminum only were relied upon for the clean-up action therein. Phosphorus may be used as an auxiliary clean-up agent, if desired.

The mount may then be sealed into the bulb and the bulb cold exhausted to a moderate vacuum, that is, it may be exhausted Without the usual heat treatment. The plate is then heated, preferably by induction or electron-bombardment, to a temperature high enough to drive off occluded gases therefrom. While the plate is heating, the aluminum thereon will first melt and then vaporize and actively clean up residual gases in the=bulb as well as occluded gases which may be driven off from the plate and other parts of the device during heating of the same.

When the plate is first inductively heated, as by means of high-frequency applied to a surrounding coil, flashes of light will be emitted in the residual gases and occluded gases driven from the parts of the device and the operator can judge when the process of cleaning-up such gases is complete by the dying out and eventual discontinuance of the flashes given in the interior of the bulb.

By notin the appearance of the bulb with respect to t e light flashes therein, the operator can judge just how far to carry the process of heat-treating the plate and vaporizing the aluminum therefrom and, in some instances, it may be found unnecessary to entirely vaporize the aluminum from the plate. It will be found that a small mirror-like coating will be prgduced on the bulb by an excess of aluminum, the extent of such coating depending on the excess in the bulb. This coating may be readily restricted to a small proportion of the surface of the bulb so thatthe contents thereof may be easily visible, instead of being almost or completely obscured, as when magnesium alone is used as a clean-up agent. It has also been found that aluminum acts much more eificiently than-magnesium, for the purpose of cleanini-[up hydrogen.

y inventlon will be better understood by referring to the accompanying drawing the single figure of which is a side elevation of a radio or electron device, part1 in section, surrounded by a coil for in uctively heatin the same, said coil, shown in section, eing diagrammatically shown. connected to a source of high-frequency current.

The radio or electron device 1 comprises abulb 2 with a flare 3 sealed therein. Supported on the flare 3 is an electrode pr plate 4, another electrode or grid 5 and an electron-emitting filament 6, together forming Lead-in wire 7 connects to the plate 4 and lead-in wire 8 to the rid 5. The filament 6 is supplied with lea ing-in wires 9 and 11 for suitably energizing the same. Plate 4 is preferably constructed of molybdenum, tungsten, I

Filament 6 is formed of an oxide-coated platinum-iridium wire or of athoriated or pure tungsten wire or any other material suitable for emitting electronsQf I Prior to its introduction into the bulb, the plate 4 preferably has applied thereto a thin sheet or foil 12 of aluminum or an alloy thereof. Magnesium, phosphorous or a similar clean-up agent, may be used in addition to secure the benefit of an early clean-up action as before explained. The ortion12 of aluminum may be applied to t e plate 4 in any suitable manner, as by welding or pasting thereon by means of an amyl-acetate so.- lution of nitro-cellulose or by applying aluminum powder thereto in the form of a paint. The bulb 2 may be cold-exhausted on the usual type of oil pump to obtain a moderate vacuum therein, such as a vacuum ranging from about 1 to 100 microns.

A coil 13 suitably connected to a highfrequency generator 14 or other suitable the plate and other metallic parts of the device 1 and also in the residual gases in the bulb 2. These induced currents will heat up the plate and other metal parts of the device and cause the residual gases in the bulb to glow or flash brightly until the plate 4 becomes highly heated and the occluded gases therein are driven off. When the tempera ture is sufliciently high, the aluminum 12 melts, vaporizes and efficiently cleans-up the residual gases in the bulb, as well as those di'iven off during the heat-treatment of the p ate.

The glow in the interior of the bulb will then disappear, thus indicating that the gases in the bulb have been eliminated. Any other suitable method of heating the plate 4 may beused instead of the inductive heatin heretofore described. For example, the ament 6 may be heated to an electron-emitting temperature by passing 'an electric current therethrough and the' 'p'late' 4 heated by electronbombardment by impressing a high potential between said heated filament and the plate.

A mirror of aluminum will be formed on the side of the bulb nearest to the location of Y that a sim-' l Ull any other evacuated device and that the construction of the radio bulb and the proportion of aluminum in the strip 12 and the method of application thereof, either in the main tube or in a side bulb, in which the clean-up may be effected, may be varied within the spirit and scope of my invention, as de-. fined by the appended claims.

What is claimed is:

1. The method of evacuating an electron device or the like includinga plate, comprising attaching a piece of aluminum to said plate, sealing the plate into a bulb, exhausting said bulb'to a moderate vacuum, heating said plate to drive oil occluded gases therefrom and continuing said heating until the aluminum thereon is vaporized and eliminates the residual gases in the device.

2. The method of evacuating a radio device or the like including a plate, comprising fastening to said plate a clean-up agent composed at least in part of aluminum, sealing the plate into a bulb, creating only a moderate vacuum in said bulb, and inductively heating .said plate to a high temperature to first drive off the occluded gases and subsequently to vaporize the aluminum thereon t-c eliminate the residual gases and those driven off by the heat-treatment.

3. The method of exhausting a vacuum device comprising creating only a moderate vacuum therein and then developing a high vacuum in the same by vaporizing therein a material such as magnesium and then a material consisting, at least in part, of alummum.

4. The method of evacuating a device including a plate ina bulb comprising attaching a piece of alun rum and a piece of mag nesium to said plate, exhausting the bulb to create a moderate vacuum therein and heating the plate by high-frequency induction until the magnesium is vaporized, to elimi-.

nate residual gases in the bulb and then the aluminum is vaporized, at least in part, to eliminate residual gases in the bulb and also occluded gases driven oil from the plate upon heating the same, whereby a high vacuum is obtained in said bulb.

' 5. The method of evacuating a device in cluding a plate in a bulb comprising attaching'a piece of aluminum and a piece of more volatile material to said plate as clean-81p -agents, exhausting the bulb to create a m erate vacuum therein and heating the plate until the more volatile material thereon is vaporized to eliminate residual gases in-the bulb and then the aluminum is vaporized, at least in part, to eliminate residual gases in the bulb and also occluded gases driven off from the plate upon heating the same whereby the plate is given a more thorough heat 7 treatment without a consequent relatively large increase in pressure therein than is possible wit-h the use of only one clean-up agent.

6. An electron discharge device comprising an envelope from which the gas has been' removed to at least a moderate degree, an electrode therein composed of a metal having a melting temperature above the vaporiza-' t-ion temperature of aluminum and a quantity of alumim m attached to said electrode in a condition to e vaporized upon heating of the electrode.

7. An electron discharge device comprising an envelope substantially free from common gases, an electrode therein composed of molybdenum and a quantity of aluminum HARVEY CLAYTON REN'I'SCHLER. 

